1. Field of the Invention
The present invention generally relates to lenses. More specifically, the present invention provides an insert having a diffractive region that can be embedded into any host lens material to form a multifocal lens.
2. Background Art
There is a desire to improve the performance and cosmetic appeal of multifocal lenses. Traditional multifocal lenses, such as bifocal and trifocals, suffer from a number of disadvantages. As an example, many traditional multifocal lenses have a visible discontinuity separating each vision zone. Blended multifocals can reduce the visibility associated with these abrupt discontinuities but generally at the cost of rendering the blend zones optically unusable due to high levels of distortion and/or astigmatism. Traditional progressive lenses can provide multiple vision zones with invisible boundaries and no image breaks but these lenses typically have narrow vision zones and are associated with large amounts of unwanted astigmatism.
Diffractive optical structures have many advantages over refractive optical structures and can reduce the visibility of discontinuities between vision zones when used to construct multifocal lenses. However, lenses using diffractive optical structures to date have suffered from a number of compromises including severe chromatic aberration due to dispersion and ghosting due to poor diffraction efficiency.
Accordingly, what is needed is a multifocal lens that exploits the advantages of diffractive optical structures to provide less visible discontinuities while additionally reducing vision compromises commonly associated with diffractive optics.